Imaging devices have been proposed that perform focus detection of an imaging lens with a phase difference detection method, using a two-dimensional image sensor in which a micro lens is formed in each pixel.
In Japanese Patent Laid-Open No. 58-24105, an imaging device using a two-dimensional image sensor in which a single micro lens and a photoelectric conversion unit divided into a plurality of parts are formed in a single pixel is disclosed. Pupil division is performed as a result of the plurality of photoelectric conversion units being configured so as to receive light from different areas of the exit pupil of the imaging lens through the single micro lens. Focus detection is performed by deriving the difference between images from signals resulting from light received by the individual photoelectric conversion units, and an imaging signal is acquired by adding together the signals resulting from light received by the individual photoelectric conversion units. Also disclosed besides focus detection is enabling display of a three-dimensional image by displaying the signals resulting from light received by the photoelectric conversion units on the right side and the photoelectric conversion units on the left side of each pixel as parallax signals.
In Japanese Patent Laid-Open No. 2000-156823, an imaging device in which plural pairs of pixels for focusing are disposed in a two-dimensional image sensor consisting of a plurality of pixels is disclosed. Pupil division is performed as a result of each pair of pixels for focusing being configured so as to receive light from different areas of the exit pupil of the imaging lens, using a light-shielding layer having an opening. An imaging signal is acquired with pixels for imaging disposed over a large portion of the two-dimensional image sensor, and focus detection is performed by deriving the difference between images from the signals of pixels for focusing disposed over a portion of the two-dimensional image sensor.
In focus detection with the phase difference detection method using a two-dimensional image sensor, focus detection accuracy depends greatly on the pupil intensity distribution (pupil division performance) of the pixels for focusing. Accurate focus detection can be performed by increasing the peak intensity and narrowing the half-value width of the pupil intensity distribution of the pixels for focusing.
However, there is a problem in that variation occurs in the pupil intensity distribution of the pixels for focusing due to positional production tolerance of the components constituting the image sensor, resulting in focus detection accuracy and parallax signals that lack stability.